Questions tagged [virtual-machines]

A virtual machine (VM) is a completely isolated guest operating system installation within a normal host operating system. It is a software implementation of a machine (i.e. a computer) that executes programs like a physical machine.

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Is it possible to make Nginx listen to different ports?

I created one Nginx with one Linux Azure VM, is it possible to make nginx listen to different ports so that when I change the port number, the content would be different. I found there would be a ...
billcyz's user avatar
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133 votes
4 answers
48k views

Why do we use a OS Base Image with Docker if containers have no Guest OS?

I've just started to study Docker and there's something that's being quite confusing for me. As I've read on Docker's website a container is different from a virtual machine. As I understood a ...
user1620696's user avatar
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101 votes
6 answers
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What range of MAC addresses can I safely use for my virtual machines?

I want to assign my virtual machines MAC addresses so that I can configure DHCP reservations for them so that they always get the same IP address regardless of which host hypervisor they are running ...
Chris Magnuson's user avatar
72 votes
16 answers
296k views

How do I know if I'm working on a Virtual Machine or not?

Is there a way to know if the Windows machine I'm working on is virtual or physical? (I'm connecting with RDP to the machine. If it's a virtual machine it is working and handled by VMWare).
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67 votes
3 answers
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Is a VM with 2 CPUs really faster than one with 4 CPUs?

Our IT created a VM with 2 CPUs allocated rather than the 4 I requested. Their reason is that the VM performs better with 2 CPUs rather than 4 (according to them). The rationale is that the VM ...
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64 votes
9 answers
186k views

Creating a virtual machine in VirtualBox from a physical one

Is there any way to create a virtual machine that you can use in VirtualBox from a physical installation that you have? For instance, if I have Windows XP installed on a physical computer and want to ...
DHamrick's user avatar
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34 votes
12 answers
139k views

Is it possible to setup a virtual machine inside another virtual machine

I've been playing with virtual machines lately, and I wondered if I could run a virtual machine inside a virtual machine. Is this possible? Is it practical?
Tester101's user avatar
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29 votes
4 answers
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Why VM snapshots are affecting performance?

I read in one of the VMware KB articles that snapshots will directly affect VM performance. But my team keeps asking me how snapshots can affect performance. I would like to give them solid reason ...
Samselvaprabu's user avatar
27 votes
1 answer
43k views

KVM and Libvirt - How do I hotplug a new virtio disk?

I am trying to hot-add a file-based disk to a running KVM virtual server. I've created a new disk from scratch using the command dd of=/home/cloud/vps_59/test.img bs=1 seek=5G count=0 and I was ...
Daniele Testa's user avatar
27 votes
4 answers
903 views

Will virtualizing a server mean another OS layer to patch and update, more work and greater risk?

I've done a search and have not found anything addressing issues regarding patching and system updates. I've got guidelines that say servers need to have necessary patches. If I have a VM host then ...
user127379's user avatar
26 votes
7 answers
87k views

mount.nfs: access denied by server while mounting

On my Ubuntu system, I have this line in /etc/fstab: myserver:/home/me /mnt/me nfs rsize=8192,wsize=8192,timeo=14,intr When I do sudo mount -a I get: mount.nfs: access denied by server while ...
JoelFan's user avatar
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26 votes
1 answer
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Why Are There Only 65,535 Ports, and Will We Ever Have More? [closed]

I understand the original reasoning behind having 65,535 ports per IP address: this is the highest number that can be represented by a 16-bit, or 2-byte, number, and it wasn't conceivable that ...
trysis's user avatar
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26 votes
5 answers
2k views

Is there a reason to give a VM a round base-2 amount (2048MB, 4096MB, etc) of memory?

The title pretty much says it all, is there any advantage to giving a VM 2048MB of memory instead of rounding to base-10 and doing 2000MB?
Nate's user avatar
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25 votes
10 answers
58k views

Running 100 virtual machines on a single VMWare host server

I've been using VMWare for many years, running dozens of production servers with very few issues. But I never tried hosting more than 20 VMs on a single physical host. Here is the idea: A stripped ...
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25 votes
2 answers
23k views

When shall I use linked vs full VM clones?

I've seen documentation for the Full and Linked virtual machine clones, but I can't seem to fully understand when I should use one over another. I see that the full clone creates a copy of the VM, but ...
c00000fd's user avatar
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24 votes
11 answers
40k views

Sync LVM snapshots to backup server

I have a number of Xen virtual machines running on a number of Linux servers. These VMs store their disk images in Linux LVM volumes with device names along the lines of /dev/xenVG/SERVER001OS and so ...
David Hicks's user avatar
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23 votes
17 answers
3k views

Virtualization Pitfalls/Lessons Learned

What are some pitfalls or lessons learned after converting existing hardware to a virtualized environment? Is there anything you tried to virtualize but will never do again?
Bob's user avatar
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23 votes
2 answers
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Is it safe to mount the same partition to multiple VMs?

I'm using ubuntu 20.04 with Xen Hypervisor. On my machine I have an SSD that hosts my VM images, and then four sata drives which I have data on. My current set up is to mount the data on my domain0 ...
curios's user avatar
  • 363
22 votes
3 answers
62k views

Cloning Virtual Machine On Azure, keeping existing

There doesn't seem to be a straight answer online about this. I have an existing Virtual Machine on Azure and I want to clone it to another region in case my existing server goes down. It needs to be ...
exposure's user avatar
  • 283
21 votes
4 answers
5k views

Why do cloud compute instances spin up VMs and not containers?

In AWS for example, when I spin up a new EC2 instance, it loads up a new VM, then populate the VM with a container image. This is the reason why spinning up new EC2 instances take 60-90 seconds to ...
user3667125's user avatar
21 votes
6 answers
44k views

How to attach a virtual hard disk using VBoxManage?

What is the best method for setting the virtual hard drive (VDI) of the primary controller for an existing virtual machine? Does the syntax change if the VDI is really a child differencing disk of ...
Adam's user avatar
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21 votes
6 answers
21k views

How do I get /dev/random to work on an Ubuntu virtual machine?

Apparently, /dev/random is based on hardware interrupts or similar unpredictable aspects of physical hardware. Since virtual machines don't have physical hardware, running cat /dev/random within a ...
Nick's user avatar
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20 votes
2 answers
7k views

understanding relationship between Qemu and KVM

What is the difference between KVM and Qemu? As I understand, latter is able to provide "user mode emulation" which means that one can run a single executable built for some other architecture like ...
Martin's user avatar
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19 votes
5 answers
18k views

So really, what is the overhead of virtualization and when should I be concerned?

I'm searching for good rules of thumb to understand when NOT to virtualize a machine. For example, I know that a fully CPU-bound process with near 100% utilization is probably not a good idea to ...
kvista's user avatar
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19 votes
5 answers
1k views

Can a VMWare Server 2.0 virtual machine be "unvirtualized" to physical hardware?

We have a number of VMWare Server 2.0 virtual machines that were created using VMWare Converter (It copies a physical machine to a virtual machine). If we need to convert the virtual machine back to a ...
Jonathon Watney's user avatar
18 votes
5 answers
1k views

Is there a way to have a virtual machine only have one core yet use three cores on the host machine? [duplicate]

Possible Duplicate: Can a single Virtual Core on a VM use more then 1 physical core? I'm a co-owner of a Minecraft server that is getting rather large each day, but as we get bigger we're running ...
bradleyhilton's user avatar
18 votes
9 answers
49k views

Hyper-V vs. ESXi vs. XenServer

Can anyone share their experiences (for example, this was great! This failed miserably!) with using the Hyper-V, ESXi, and XenServer virtualization platforms? Cost? Management? features? Handling load ...
Bart Silverstrim's user avatar
17 votes
3 answers
18k views

How is memory allocated in ESXi server?

We have an ESXi 4.1 server with 48 GB RAM. For each VM, we are allocating 4GB of memory. Since the server will have 13 virtual machines, my manager thinks this is wrong. I am going to explain to ...
Samselvaprabu's user avatar
16 votes
7 answers
30k views

How to setup /etc/issues to show the IP address for eth0

I've got a couple of linux virtual machines with bridged interfaces, and I'd like the IP address of the machine to show up after the machine boot (in the login, where it usually shows the release and ...
Bruno Lopes's user avatar
16 votes
5 answers
7k views

Defrag in Windows VM?

I've read conflicting advice on this issue so thought I'd ask here. Should I be running a scheduled defrag within my VM?
SteB's user avatar
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16 votes
3 answers
34k views

PING icmp open socket: Operation not permitted in vserver

I am running a vserver environment with several virtual machines. A single VM has the following problem: $ ping 8.8.8.8 ping: icmp open socket: Operation not permitted $ ls -l $(which ping) -rwsr-xr-...
rexkogitans's user avatar
16 votes
3 answers
26k views

MSTSC: Black Areas on Remote Desktop

I'm connecting from Windows Server 2012 R2 to Hyper-V virtual machine running Windows 8.1 via RDP (mstsc.exe). The VM is hosted on the same machine from which I'm connecting. Everything was fine until ...
Alexander Abakumov's user avatar
16 votes
2 answers
17k views

Running containers inside a virtual machine?

It is my understanding that containers are much more lightweight than VMs because they do not virtualize the hardware but instead just isolate the software running in them from software running in ...
Chris L's user avatar
  • 323
16 votes
4 answers
7k views

Vagrant shared folder and file change events

I have ubuntu virtual machine that I'm accessing through Vagrant. On my host (Mac OSX), there is a folder with couple of files, that I share to virtual machine. In that virtual machine, I want to use ...
rdamborsky's user avatar
16 votes
2 answers
27k views

Renaming an Azure VM

I am looking to rename an Azure VM. I have copied a VM from one subscription to another using this guide: http://blogs.msdn.com/b/microsoft_press/archive/2014/01/29/from-the-mvps-copying-a-virtual-...
Nick Chambers's user avatar
15 votes
15 answers
46k views

Web based KVM management for Ubuntu

We've got a single Ubuntu 9.10 root server on which we want to run multiple KVM virtual machines. To administer these virtual machines I'd like a web based KVM management tool, but I don't know which ...
Tim's user avatar
  • 215
15 votes
2 answers
51k views

Running Mac OS X on Hyper-V

I have my workstation setup with a Windows Server 2008 running Hyper-V. Now I really want to install OS X for testing purposes. Have anyone had any success running Mac OS X in an Hyper-V environment? ...
Thomas's user avatar
  • 181
14 votes
5 answers
92k views

virsh: VM console does not show any output

I have a VM which I can start with virsh. According to virsh dumpxml VM1, this is the allocated pty: <serial type='pty'> <source path='/dev/pts/6'/> <target port='0'/> <...
blueFast's user avatar
  • 4,330
14 votes
2 answers
797 views

How to get free space from mounted drive Redhat 7

In our VM infrastructure, we have clustered hosts going to a SAN. What i am trying to figure out is how much "white space" is left over when deleting files within our Redhat servers. On our Windows ...
Anthony Fornito's user avatar
14 votes
6 answers
81k views

How to decrease the size of a KVM virtual machine disk image?

How do you decrease or shrink the size of a KVM virtual machine disk? I allocated a virtual disk of 500GB (stored at /var/lib/libvirt/images/vm1.img), and I'm finding that overkill, so now I'd like ...
Cerin's user avatar
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13 votes
11 answers
11k views

Any way to run Linux as a Virtual Machine on top of Windows so can have best of both worlds?

Since Linux has a lot of useful tools, while Windows has a lot of apps (like Chrome), instead of buying another machine to run Linux, is there a way to run it as a Virtual Machine on the PC? The ...
13 votes
5 answers
3k views

Renting a dedicated, but getting a VPS. How to detect? [duplicate]

When renting a dedicated server, how can one be certain than he/she is not getting a VPS or some other virtual machine variant instead of a true dedicated hardware box? Which checks can be run (...
mr-euro's user avatar
  • 858
13 votes
8 answers
874 views

What is this server doing?

I have a bunch of linux virtual servers left over from a previous IT department. They have names like 'magic' or 'stuff'. I'm not quite sure what they're doing...or if I need them... How would you ...
blsub6's user avatar
  • 1,151
13 votes
4 answers
14k views

Can a virtual machine (VM) "hack" another VM running on the same physical machine?

Questions: if a VM is corrupted (hacked), what do I risk on others VMs running on the same physical machine? What kind of security issues is there between VMs running on the same physical host? Is ...
Totor's user avatar
  • 2,996
13 votes
4 answers
44k views

Is it dangerous to change the value of /proc/sys/net/ipv4/tcp_tw_reuse?

We have a couple of production systems that were recently converted into virtual machines. There is an application of ours that frequently accesses a MySQL database, and for each query it creates a ...
Sagar's user avatar
  • 534
13 votes
4 answers
18k views

Backing up qcow2 kvm guests

I can't find any good info on backing up qcow2 kvm guests. I'm not really interested in the guests running state, only the file system. This question suggests using savevm but that creates a snapshot ...
EightyEight's user avatar
13 votes
2 answers
12k views

Entropy on virtual machines

As you might know that it's not as easy to generate entropy on a virtual machine as on a "normal" pc. Generating a gpg-key on a virtual machine can take a while, even with the correct tools. There ...
dbanck's user avatar
  • 413
13 votes
3 answers
41k views

Having Mac OS X on a XEN virtual machine

Is it possible to have Mac OS X guest on a XEN host? If yes, how? There are difference for Mac OS X Server? In particular I'm interested in the installation of a testing Mac OS X Server inside a ...
drAlberT's user avatar
  • 11k
12 votes
2 answers
5k views

Windows Server 2008 R2 64-bit memory leak

I´m having trouble in one of my office servers. It´s a virtualized Windows 2008 R2 Server with 6GB RAM memory. It only has Microsoft SQL Server (memory assigned maximum = 3GB), and just a software ...
Guillermo Zooby's user avatar
12 votes
4 answers
6k views

What happens when a physical machine fails in a virtual environment? [closed]

I'm getting started with virtualization so bear with me. In virtual environments applications run in a hypervisor's layer. So a single physical machine could have many virtual machines on it running ...
Sherif's user avatar
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